The Taiwanese Patent Serial No. 81208343 discloses a lock for incapacitating the motorcycle disk brake. As shown in FIG. 1, the lock comprises a lock body 1 provided with a first portion 2 having a locking hole 3. Such a prior art lock as described above is defective in design in that the locking hole 3 can be clogged by dust deposited therein. The clogged locking hole 3 obstructs the entry of the locking bolt 4 into the locking hole 3.